Hydraulic slack adjuster



P 24, 1934- J. o. ALMEN ET AL ,95

HYDRAULIC SLACK ADJUSTER Filed n5. 8, 1932 2 Sheets-Sheet 1 ya/m 0. dimer? &

(image .7. fizzy.

14 3% Z I biaqw April 1934- J. o. ALMEN ET. AL 1 5,

HYDRAULIQ SLACK ADJUSTER Filed Feb. 8. 1932 2 Sheets-Sheet 2 wig??? 6 SH 11W gig folk: 0412mm & Gan g1: Zen}.

Patented Apr. 24, 1934 1.955.786 HYDRAULIC SLACK ADJUSTER John 0. Almen, Royal Oak, and George P. Berry,

Detroit, Mich., assignors to General ,Motors Research-Corporation, Detroit, 'Mich., a corpo ration of Delaware Application February 8, 1932, Serial No. 591,586

Claims.

This invention has to do with an improvement upon tbeinvention described and claimed in the application of J. O. Almen, Serial No. 187,343, filed April 28, 1927.

5 In that application there is disclosed a valve slack adjuster consisting of a hydraulic dashpot so arranged with respect to the valve mechanism as to continually tend to take up slack in the system, but at the same time the dashpot is so 10 cated as to be relieved from the very heavy valve operating pressure. This is accomplished in the Almen application by using the dashpot as a yielding abutment for a lever arm rigidly securedto an eccentric bushing. The Almen invention hasbeen extensively used on overhead valve en'- gines, but is not well adapted, in the form shown, to. the conventional type of valve mechanism used on L-head engines. The present invention has to .do with the application of the principles Y Figures 6 and 'l are detail views showing fur-- ther modified arrangements.

In Figure 1 we have shown a portion of a conventional L-head engine provided with poppet valve 10, held on its seat by spring 12. A portion of the camshaft is shown at 14 provided with cam 16' which engages push rod 18. The push rod 18-comprises an internally threaded member 20 and an externally threaded member 22 fitted therein, the angle of the threads being such that the parts of the tappet may -.be collapsed when endwise pressure is applied to them. Of course, the angle may be so selected as to interpose whatever amount-of frictional resistance is desired. To the upper part of the member 22 is secured a clamping collar 24 having anintegral arm 26 which terminates in an enlarged portion 28 adapted to engage the end 30' of the plunger 32 working in hydraulic cylinder 34. The spring 36 urges the piston 32 outwardly of the'cylinder,

and a spring pressed check valve 38, of any suitable design, may be mounted in the piston as shown, or in the cylinder to admit oil to the hydraulic chamber. The chamber may be sup- 65. plied with oil either by connection with the lubricating system, as shown at 40, or by drip from lubricated parts of the valve gear. The member 20 is preferably restrained from rotation by a key, such as indicated at-42. a

In the operation of this construction, when the cam 16 lifts the tappet 18 the motion is resisted by the valve spring 12 and the endwise pressure on the parts 20 and 22 tends to shorten the overall length of the tappet because of the reversible character of the screw threads. Rotation of the part 22 is resisted by the plunger 32 and the body of oil trapped in the bottom of the cylinder 34. Actually, there will be a slight leakage of oil between the cylinder and its piston. During any movement of the valve the end 28 of the arm 26 7 will, of course, have sliding contact with the piston 30. When the cam 16 passes out from under the tappet the valve spring 12 will return the valve 10 to its seat, and the two part tappet will be relieved of its pressure. There will now be a slight amount-of slack in the system as a consequence of the leakage of -oil from the cylinder 34 during theoperating stroke. The-spring 36 will consequently force the piston 32 out of the cylinder whereupon the valve .38 will open to admit additional oil into the chamber. This adjustment of x slack will take place during each cycle of operation of the valve, and will permit any further ad- 'justment that may be required by change in temperature of the parts.

In Figure 3 we have shown a slight modification.

. Here, in place of a threaded connection, we have shown the parts 18' and 22 of the tappet pr0- isrizded withcontacting spiral cam surfaces 50 and In Figures 4 and 5 wehave' shown a further modification. Here, the tappet member 22" is provided-with-a collar 54 having 2. lug 55 engaged by the arm 56 of lever 53. The long arm 60 of the lever engages piston32 in cylinder 34. The parts of the dashpot may be the same as previously described.

The advantage of this construction is that the dashpot is in upright position so that it may be more easily kept full by drip from lubricated valve parts.- The lever likewise introduced mechanical advantage which further reduced the pressure on the oil in the dashpot, and permits the use of a steeper thread between the parts of the dashpot, if desired. As shown in Figure 5 the levers 58 may be mounted on a common-pivot 61 extending between adjacent valves, thereby reducing the cost of construction. Obviously by using reversed threads on adjacent tappets the levers would be 110,

mounted close to each other on short stub shafts extending between adjacent valves only.

In Figure 6 we have shown diagrammatically a further'modification. Here, the piston 32 has a bevelled end 60 engaging a similarly bevelled end on plunger 62 which may be guided in aperture 64 in an extension of the tappet guide. The other end of the plunger 62 engages abutment 66 on the tappet member 22, and urges it as before in a direction to take up slack.

In Figure 7 we have shown a further modification. Here, the dashpot 34 is arranged at an angle to the vertical and directly engages the key 66 on the tappet part 22. The inclination of the dashpot 34, as shown, is such so that the hydraulic chamber will-at all times be full of oil. In this form of the invention, as well as the form shown in Figure 6, there is the disadvantage that there 1 is considerable side thrust on the pistons 32.

Among obvious modifications of our invention may be noted the following: If desired the dashpot piston may be stationary and the cylinder may be movable and act upon the rotary threaded part of the tappet. The dashpot may be mounted on any suitable support, either the tappet guide, the bottom of the valve chamber, or the cylinder wall. In the construction shown in Figure 4, it is obvious that instead of providing the pivot 58 the lever may be fulcrumed in an aperture in the tappet guide. The arm 28 may be secured to the tappet member 22 in any desired way. The adjustable clamping collar 24 has the advantage that it may be shifted about the axis of the tappet as desired. This is particularly convenient in making the initial adjustment.

In all of these constructions it will be noted that a part carried by the tappet has sliding engagement with either the end of the dashpot plunger or some member actuated thereby. These contacting surfaces will be well lubricated. Owing to the mechanical advantage introduced by the threaded parts of the tappet the force tending to rotate the plunger part 22 will be relatively small so that the pressure between the parts in sliding engagement will be slight. Thus, as in the prior Almen application, the dashpot is subjected to but a fraction of a valve operating pressure so that there is less leakage past the dashpot piston, and there will likewise be less difiiculty with air which may find its way into the cylinder.

If desired the dashpots may be provided with a flexible or rigid cover such as shown at 68 in Fig. 6. By applying the cover'when the dashpot is full of oil and immersed in oil and oil may be sealed within the dash pot and air cannot get in.

Where the cover does not serve as a guide, it may take the form of a flexible diaphragm such as shown in Bollee 1,062,580.

We claim:

1. In a slack adjuster the combination of operating mechanism including a plurality of reciprocating members having engaging cam faces so that upon rotation of one of said members in one direction with respect to. the other their overall length is increased and upon rotation of said member in the opposite direction with respect to the other their overall length is diminished, means urging said member in' a direction to increase said overall length to take up slack in the system, and stationary means cooperating with .said. member for damping reverse movement thereof.

2. In a slack adjuster the combination of operating mechanism including a plurality of reciprocating members having engaging cam faces so that upon rotation of one of said members in one direction with respect to the other their overall length is increased and upon rotation of said member in the opposite direction with respect to the other their overall length is diminished, and a stationary hydraulic dashpot having a spring urged fluid-cushioned part tending to rotate said member in a direction to take up slack in the system.

3. In a slack adjuster the combination of operating mechanism including a plurality of reciprocating members having engaging cam faces so that upon rotation of one of said members in one direction with respect to the other their overall length is increased and upon rotation of'said member in the opposite direction with respect to the other their overall length is diminished, and a stationary hydraulic dashpot urging said member in a direction to increase said overall length 10.5

ciprocating members having threaded engagement with each other so that upon rotation of one of said members in one direction with respect to the other their overall length is increased and upon rotation of said member in the opposite direction with respect to the other their overall length is diminished, means for preventing rotation of said other member,- and a stationary hydraulic. dashpot having a fluid cushioned part in sliding engagement with saidmember and tending to rotate it in a direction to increase said overall length and take up slack in the system.

5. In a slack adjuster the combination. of operating mechanism including a plurality of reciprocating members having threaded engagement with each other sothat upon rotation of one of said members in one direction with respect to the other their overall length is increased and upon rotation of said member in the opposite direction with respect to the other their overall length. is diminished, means for preventing rotation of said other member, and a stationary hydraulic dashpot having a fluid cushioned part in sliding engagement with said member and tending to rotate it in a direction to increase said overall length and take up slack in the system,

and a lever interposed between said member and the part.

JQHN O. ALMEN. GEQRGE P. BERRY. 

